Surf board and adhesive film for surf board

ABSTRACT

The present invention provides a surfboard improved in a movement performance such as a speed or a change of direction, etc. at the time of sliding on water, as compared with a conventional surfboard. The surfboard is so constructed that a tough and soft synthetic resin film  7  having a surface smoothness and patterned along to the contour of the rear area  2   a  of the water-contact bottom surface  2  of a surfboard  1  or the contour of both side faces  9   b  and  9   b  of a fin  9  is adhered either to the rear area  2   a  of the water contact bottom surface  2  of the surfboard  1  or to both side faces  9   b  and  9   b  of the fin  9  attached thereto, or to both of the rear area  2   a  and both side faces  9   b  and  9   b  of the fin  9,  through an adhering agent such as a bonding agent or an adhesive agent. As the synthetic resin film  7  for adherence, such a one that a coated face  8  of the adhesive agent is applied to the rear surface thereof in advance is preferably used.

TECHNICAL FIELD

The present invention relates to a surfboard aimed at improving a movement performance and a change of direction, etc. thereof and to an adhesive film for a surfboard.

BACKGROUND ART

A conventional surfboard comprises a foam core having a super high density and formed into a desired contour of surfboard and an outer skin formed of a reinforced plastic resin, typically a plastic reinforced with a fiber cloth of such as glass fibers etc. and integrally laminated on the surface of the foam core. And, there has been preferably in general to finish it by a polishing treatment in order to in order to decrease a water flow resistance of the outer skin as much as possible.

Also, a single fin or plural fins is/are to be attached to the rear area of the water contact bottom surface of the surfboard is produced in almost the same manner as the case of production of the above-mentioned surfboard and has almost the same construction as the surfboard, and as a fiber cloth embedded in the reinforced plastic constituting the outer skin thereof, there has been used, besides the glass fiber cloth, a carbon fiber cloth or a mixed fiber cloth made of both of glass fibers and carbon fibers.

However, when the surface of the conventional surfboard and that of the fin thereof as mentioned above are observed using an optical laser measurement apparatus, it has been found that their surfaces are unexpectedly rough and are large in a water flow resistance.

In view of the results of the above-mentioned study, an object of the present invention is to provide a surfboard that is decreased in a water flow resistance to be improved in a movement performance such as a speed and a directional change or the like, as compared with the conventional surfboards.

DISCLOSURE OF THE INVENTION

The present invention lies in a surfboard characterized in that a tough and flexible synthetic resin film having a surface smoothness and patterned to be adaptable to be adhered to a rear area of a water contact bottom surface of a surfboard is adhered through an adhering agent such as a bonding agent or/and an adhesive agent to the rear area of the water contact bottom surface or/and both side faces of a fin. Consequently, each of the respective surfboards according to the present invention, owing to the surface smoothness of the foregoing Synthetic resin film adhered to the rear area of the water contact bottom surface thereof or/and to that of both the side faces of the fin, there can be obtained the surfboards which is improved in a movement performance such as a speed or a change of direction, etc. as compared with the conventional surfboards. The effect of the improvement in the above-mentioned movement performances is increased in the order of a case of adhering the synthetic resin film to both the side faces alone of the fin, a case of adhering it to the rear area alone of the water contacting bottom surface, and a case of adhering it to both of the side faces of the fin and the rear area.

Further, in the present invention, as for the synthetic resin films for adherence, there can be used any desired synthetic resin film selected from a group of polyester resin, polyamide resin, polyethylene resin, polypropylene resin, polyacrylate resin, polycarbonate resin, ABS resin, fluorinated resin and polyvinyl chloride resin. These synthetic resin films are preferable, because they are excellent in mechanical strength, water resistance, weather resistance, durability, impact resistance, etc.

Furthermore, as to the synthetic resin films used in the present invention, any one having such a degree of the surface smoothness that is less than 0.2μ in the high and low height difference throughout the whole surface thereof is preferably used.

Furthermore, in the present invention, in producing the surfboards according to the present invention, in order that the adhering work of the synthetic resin film for adherence can be carried out at a high efficiency and at a low price, it is preferable to use an adhesive synthetic resin film used for a surfboard comprising a tough and flexible synthetic resin film for adherence having a surface smoothness that is patterned into a shape adaptable to adhering to the rear area of the water contact bottom surface of the surfboard or to both the side faces of the fin, an adhering face formed by coating an adhesive agent onto the rear surface of the film, and a released paper temporarily applied to the adhering face.

Furthermore, as the adhesive synthetic resin film for a surfboard according to the present invention, when there is used such a one produced by such a manner that the adhering face is formed by coating the adhesive agent partially in a regular or irregular manner so as to form a lot of air escape grooves communicating to the exterior among a lot of coated portions, there remains no bubbles between the adhering face of the adhesive film and the adhered surface of the surfboard side, so that the adhesive film can be satisfactorily adhered to the entire surface thereof.

Furthermore, as the adhesive synthetic film for a surfboard, if the adhesive film is composed of plural divided pieces, the divided pieces can be adhered to the above-mentioned specific portion(s) with a desired space left between them.

Furthermore, as the adhesive synthetic resin film for adherence used for the synthetic resin adhesive film for a surfboard according to the present invention, there may be used any kind one of a transparent (including semi-transparent) film, an opaque film, a colorless film, a colored film in a desired color, a any kind of printed films bearing a desired indication such as such as characters, designs, pictures, patterns, or combinations of such indications, or the like on the surfaces thereof, and accordingly manufacturers of surfers, distributors or consumers such as surfers can select from the above-mentioned various kinds of adhesive films and put the selected ones to their surfboards, so that their desired surfboards can be produced.

And, the manufacturers or the consumers can select from the various kinds of the adhesive surfboard films for surfboards which are different in patterns or sizes also, and after peeling off the released papers of the selected ones, put them to the foregoing specified rear portions of the conventional surfboards, so that surfboards which are different in the improved movement performances such as the improved speeds can be made according to their desire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear view of a surfboard in one embodiment of the present invention.

FIG. 2 is a magnified cross-sectional view along a line II-II in FIG. 1.

FIG. 3 is a partially cut-off front view of an adhesive film for a surfboard in one embodiment of the present invention.

FIG. 4 is a perspective view of a bottom surface of a surfboard in another embodiment of the present invention.

FIG. 5 is a partially cut-off front view of an adhesive film used for adhering to the surfboard as shown in FIG. 4.

FIG. 6 is a magnified cross-sectional view along a line VI-VI in FIG. 4.

FIG. 7 is a perspective view of a bottom surface of a surfboard of further another embodiment of the present invention.

FIG. 8 is a partially cut-off front view of an adhesive film used for adhering to the surfboard as shown in FIG. 7.

FIG. 9 is a perspective view of a bottom surface of a surfboard of further another embodiment of the present invention.

FIG. 10 is a view of a detached one of the fins shown in FIG. 9, showing the other side face of the fin opposite to one side face of the fin shown in FIG. 9.

FIG. 11 is a partly omitted front view of an adhesive sheet used for an adhesive sheet for a surfboard comprising an adhesive sheet used for adhering to fins of a surfboard shown in FIG. 7 and FIG. 8.

FIG. 12 is a perspective view of a bottom surface of a surfboard of further another embodiment of the present invention.

FIG. 13 is a front view of an adhesive film to be used for adhering to the rear area of the surfboard, showing a varied example of the adhering face in a state where a released paper is being peeled off.

FIG. 14 is a front view of an adhesive film to be used for adhering to a side face of a fin of the surfboard, showing a varied example of an adhering face in a state where a released paper is being peeled off.

FIG. 15 is a front view of a rear area of a water contact bottom surface of a surfboard of further another embodiment of the present invention.

FIG. 16 is a front view of a rear area of a water contact bottom surface of a surfboard of further another embodiment of the present invention.

FIG. 17 is a chart showing a degree of a surface smoothness of a surface of a conventional surfboard.

FIG. 18 is a chart showing a degree of a surface smoothness of one example of a synthetic resin film to be adhered to a surfboard of the present invention.

FIG. 19 is a view showing a test apparatus for comparing speeds of a surfboard in one embodiment of the present invention and a conventional surfboard, and data of comparative speed tests.

BEST MODE OF CARRYING OUT THE INVENTION

The present invention will be explained in detail with reference to accompanying drawings as follows.

FIG. 1 is a rear view of a surfboard denoted by a symbol A, in one embodiment of the present invention. According to the present invention, there is prepared a lot of patterned synthetic resin films each formed by being cut out from a large-sized, for instance, a wide and long, tough and flexible material having a surface smoothness having a surface smoothness (not shown), in such a manner that it is cut off along the contour of a rear area 2 a of a water contact bottom surface 2 of a conventional surfboard 1, specifically along the contour of the rear area extending from a tail 3 thereof to both lateral edges 4, 4, and so as to form a cut lateral crossing a right tail 4 and a left tail 4 of the surfboard 1, to form a pattern of which the right and left face shapes may become symmetrical right and left in the lateral direction of the surfboard, and, in the illustrated example, to form the pattern in which the cut lateral edge of the peripheral edges may have a V-shaped cut lateral edge, and at the same time, the pattern is punched to have a through hole 6 that is to be aligned with a fin mounting hole 5 a for a plug 5 made in advance in the bottom surface of the surfboard 1 and that is positioned on a central axis thereof. It is of course that a shape of the peripheral edges or a size of the resultant patterned synthetic resin film for adherence 7 is varied with a shape and a size of the rear area of the surfboard.

In the illustrated example, the synthetic resin film for adherence 7 thus produced is so used that an adhering agent 8 such as a bonding agent or an adhesive or sticky agent is uniformly coated on the rear area 2 a of the surfboard 1, that is, the surfboard main body 1, on such a predetermined area of the rear area 2 a that the synthetic resin film for adherence film 7 is to be applied, and the synthetic resin film for adherence 7 is press applied to the coated face 8 in such a condition that the through hole 6 thereof may be aligned with the fin mounting hole 5 a for the plug 5. Thereafter, a tab 9 a of a fin 9 is firmly press mounted, as shown in FIG. 2, in the mounting hole 5 a for the plug 5. As will be apparent from FIG. 1, the synthetic resin film 7 adhered to the rear area 2 a of the water contact bottom surface 2 of the surfboard main body 1 is adhered in such a condition that the right and left thereof may become symmetrical in the lateral direction with the central axis of the surfboard main body 1 being the center line, and, in other words, the right and left smooth surfaces equal in the shape and size may be formed, so that a surfboard A1 according to the present invention is constructed.

The conventional surfboard 1 before adhering the synthetic resin film for adherence 7 thereto is such a one preferably manufactured and used in general. Namely, it comprises a molded body 1 a which is contoured into a predetermined surfboard and is made of a foam core having an ultra high density, preferably, an urethane foam core having an ultra high density, in which a stringer 1 c made of wood in general is embedded therein along on a central axis thereof, and an outer skin 1 b made of a reinforced plastic reinforced with a glass fiber cloth, and integrally bonded to the surface of the foam core, and it is finished by polishing the surface of the outer skin in order to reduce a water flow resistance.

The fin 9 also is produced to have the same construction same as the conventional surfboard 1, and there is also a fin of which the outer skin is formed of a reinforced plastic reinforced with a carbon fiber cloth instead of the glass fiber cloth. In either case, it is in general that the conventional surfboard 1 and the fin 9 are both composed of a foam core having an ultra high density and an outer skin made of a fiber reinforced plastic.

The polished surfaces of the outer skins made of the reinforced plastics of the conventional surfboard 1 or fin 8 appears apparently smooth surfaces, but when the surfaces thereof were measured using an optical laser measurement apparatus, it has been found out by the inventor that the surfaces are triangular wavelike rough surfaces with the high and low height difference that is about 0.1 to 0.6μ per distance of 1 mm as shown in FIG. 18.

In order to improve this, the synthetic resin film for adherence 7 having the surface smoothness is adhered to the rough surface of the rear area 2 a, it has been confirmed, as will be proven by the speed tests as described later in detail, that a sliding speed of the conventional surfboard 1 is improved. Accordingly, an improvement also in a movement performance such as a change of direction of the surfboard 1 is brought about.

As for the synthetic resin film 7 used as shown in FIG. 1, for example, a tough and flexible polyethylene terephthalate resin (PET) having a thickness of about 50 to 125μ was used. When a degree of the surface smoothness thereof was measured, it has been confirmed that, as shown in FIG. 17, the height difference as a result of measurement of the surface is less than 0.2μ per distance of 1 mm with a gentle curve over the entire length as shown in the Figure, and the surface of the film is glossy throughout the entire surface thereof and has a smoothness like a mirror surface.

The PET film is excellent in all of mechanical strength, impact resistance, weather resistance, water resistance, brine resistance and heat resistance, and hardly shrinks by heat, and thus it is stable, tough and also is prolonged in a service life and is excellent as it is used for a surfboard. It is of course that the film is not limited to the PET film, and any one of other kinds of synthetic resin films may be selectively used, for instance, from a group of polyester resin, polyamide resin, polyethylene resin, polypropylene resin, polyacrylate resin, polycarbonate resin, ABS resin, fluorinated resin and polyvinyl chloride resin, and these resins are excellent in mechanical strength, water resistance, weather resistance, durability and impact resistance.

As for the adhering agent 8 which is an adhesive agent or a pressure sensitive adhesive agent for adhering these synthetic resins, as typical examples, an acrylic adhesive or an acrylic pressure sensitive adhesive agent are preferably used.

In the above-mentioned embodiment, for producing the surfboard Al according to the present invention, it comprises a step of coating the adhering agent 8 such as a bonding agent or an adhesive agent or a pressure sensitive adhesive agent to the necessary predetermined area of the rear area 2 a uniformly and equally in thickness and a step of then applying the synthetic resin film 7 to the adhering face, so that the producing work is troublesome and time-consuming and inefficient.

Now, for instance, there is prepared a lot of patterned synthetic resin films 7A for adhering to the bottom of the surfboard as shown in FIG. 3, formed to have the same pattern as the patterned synthetic resin film for adherence 7 shown in FIG. 1, by cutting out a raw material sheet comprising a wide and long large-sized synthetic resin film material having the aforementioned characteristic properties, a coating layer of an adhesive agent coated uniformly so as to have an equal thickness in the range of 20-40μ on the rear surface thereof, and a released paper temporarily applied to the coated face. In the drawings, a symbol 7 denotes a synthetic resin film 7, 8 denotes the coated face of the adhesive agent, 10 denotes a released paper, and 6′ denotes a through hole. And, at the time of producing the surfboard A1 according to the present invention, the patterned adhesive film 7A, after peeling off the released paper 10 thereof is press-applied through the adhesive surface 8 thereof to the rear area 2 a of the water contact bottom surface 2 of the surfboard main body 1 in such a manner that the through hole 6′ may be aligned with the mounting hole 5 a of the plug 5 for mounting the fin 9, so that the coating step for applying the adhesive agent to the surfboard body can be dispensed with and the surfboard A1 of the present invention can be produced at a high efficiency and inexpensively. In this case, the adhesive film 7A for adhering to the bottom surface can be provided as a merchandise and when it is adhered to the area 2 a of the tail of the surfboard 1, an improvement in the movement performance such as a speed, a directional change or the like is brought about.

FIGS. 4 and 5 show another embodiment of the present invention. The conventional surfboard as shown in these Figures is an another type of surfboard 1′ having three fins 9′ preferably used in general, and the present invention is applied to the surfboard 1′. More in detail, the surfboard 1′ is of such a type that within a rear area 2 a′ of a water contact bottom surface 2′ thereof and on the central axis of the surfboard 1′, a fin 9 is detachably mounted in the vicinity of a tail 3′, and two similar fins 9 and 9 are disposed in front of the fin 9 and on the left side and on the right side leaving equal distances from the pin 9. For applying the present invention to the surfboard 1′ of this type, there is prepared a patterned pressure sensitive adhesive film 7AB for adhering to a bottom surface so patterned as to surround only the fin 9 positioned on the central axis among the three fins 9, 9 and 9, to have a contour cut out along the tail 3′ and left and right side edges 4′ and 4′, to have a laterally extended inner edge which has a projected V-shape symmetrically at the right and left of the central axis and which crosses the side edges 4′ and 4′, and further to have through holes 6′, 6′ for passing through a pair of tabs 9 a, 9 a provided in front and rear portions of the fin 9. After the patterned adhesive film thus prepared, after a released paper 10 is peeled off therefrom, it is press-applied to the rear area 2 a under such a condition that, as shown in FIG. 6, the through holes 6′, 6′ are aligned with the pair of front and rear holes 5 a′, 5 a′ made in a fin mounting plug 5′ of the surfboard 1′, so that the surfboard A2 of the present invention is constructed.

FIG. 6 shows such a state that the fin 9 is detachably mounted in the socket. A pair of front and rear tabs 9 a, 9 a of the fin 9 are mounted in rectangular mounting holes 5 a′, 5 a′ of the socket 5′ embedded in the rear area 2 a of the surfboard A2, and the fin 9 is fixed to the socket in such a manner that the a screw 12 is driven into a threaded hole 11 against the side face thereof.

For changing the conventional surfboard for improvement into a surfboard according to the present invention, it is needless to say that it can be achieved by such a way that in such a condition that the fin 9 is once detached from the conventional surfboard, either the synthetic resin film 7 or the pressure sensitive adhesive film 7A is adhered to the rear area thereof.

FIG. 7 shows further another embodiment of the present invention. A pressure sensitive adhesive film 7C for adhering to a bottom surface is patterned so as to be in the shape of a butterfly as shown in FIG. 8, by being cut out symmetrically right and left in the lateral direction of the surfboard, as mentioned above. The size thereof has a large area enough to adhere to the disposed region surrounding the three 9, 9 and 9, as shown in FIG. 7, and also by being punch out to make three pairs of each pair of the front and rear mounting holes 5 a′ and 5 a′ for mounting the a pair of front and rear tabs 9 a and 9 a disposed in each plug 5 of each of the three pairs of front and rear tabs 9 a and 9 a of each of the three fins 9, 9 and 9.

FIG. 9 shows a perspective view of a surfboard A4 according to further another embodiment of the present invention. This embodiment is such that the pressure sensitive adhesive film 7 for adhering to a bottom surface and the pressure sensitive adhesive film for adhering to a fin which are excellent in smooth surface and tough as mentioned above have respective patterns produced by being cut out respectively along the contour of the rear area 2 a′ of the water contact surface 2′ of the conventional surfboard 1′ and that of the fins 9, respectively are adhered to both of the rear area 2 a′ and the fins 9, respectively. More in detail, as shown in FIG. 5, the pressure sensitive adhesive film 7B for adhering to a bottom surface is used, and, as shown in FIG. 4, it is adhered, after the released paper 10 is peeled off, through its adhering face 8 to the rear area 2 a′ of the water contact bottom surface 2′ of the surfboard 1′, and, on the other hand, from a wide and long acrylic synthetic resin sheet material which has a tough and glossy surface smoothness and a surface height difference of about 0.1μ, there is prepared a lot of patterned pressure sensitive adhesive films 7D for adhering to a fin by cutting out the same along the contour, that is, the peripheral edges, of the side face 9 b of the fin 9, as shown in FIG. 11, and, the patterned adhesive film, after the released paper 10 is peeled off, is adhered through its adhering face 8 to both the side faces 9 b and 9 b of the each fin 9 as shown in FIG. 10 and FIG. 11, so that the surfboard A4 according to the present invention is constructed.

FIG. 10 shows the other side face of the fin 9 opposite to one side face of the fin 9 as shown in FIG. 9.

FIG. 12 shows a perspective view of a bottom surface of a surfboard A5 of further another embodiment of the present invention. In this embodiment, the synthetic resin film 7 or 7′ for adherence according to the present invention is not adhered to the rear area 2 a of the water contact bottom surface 2 of the conventional surfboard 1′, and, instead thereof, a pressure sensitive adhesive film for adhering to a fin 7D as shown in FIG. 11, after the released paper 10 is peeled off, is adhered to both the side faces 9 b and 9 b of each of the three fins 9, so that the surfboard A5 is constructed.

FIG. 13 shows a varied example 7B′ of the pressure sensitive adhesive film for adhering to a bottom surface. FIG. 14 shows a varied example 7D′ of the pressure sensitive adhesive film for adhering to a fin. In each of the varied examples 7B′ and 7D′, the adhering face 8 of each of the pressure sensitive adhesive films is formed to have a lot of air escape grooves 13 of which both ends communicate with the external air. In the illustrated examples, a lot of the air escape grooves 13 are so provided as to be crossed with each other regularly, and longitudinally and latitudinally. However, the configuration thereof is not limited to this. A lot of air escape grooves may be formed by the longitudinal grooves alone or by the latidudinal grooves alone. In addition, though not shown, it is optional that a lot of dots of the sticky agent 8 are applied regularly or irregularly to the rear surface of the synthetic resin film 7 so as to form a lot of air escape grooves among them, for instance.

When the adhesive films 7B′ and 7D′ of this kind are adhered under pressure, after the released paper 10 and 10 are peeled off, to the above-specified positions, the air present between the adhered films and the surfaces applied with the films are expelled to the exterior through the air escape grooves 13, 13, . . . , so that there remains no bubbles therebetween, and accordingly the respective synthetic resin films are adhered satisfactorily throughout the entire applied surfaces.

The patterned synthetic resin film 7 and the patterned synthetic resin film which are not coated with the pressure sensitive adhesive agent on the rear surface and therefore are to be adhered, after coating of an adhesive agent or a pressure sensitive agent, to the rear area 2 a of the water contact bottom surface 2 or the side faces 9 b of the fin 9 of the conventional surfboard main body 1′, or the pressure sensitive adhesive film for adhering to a bottom surface or the pressure sensitive adhesive film for adhering to a fin, are not always limited to be formed of a single sheet. For example, as shown in FIG. 15, the pressure sensitive adhesive film 7A for adhering to a bottom surface composed of two patterned sheets, that is, two divided pieces 7 a′ and 7 a′ prepared by cutting out along the contour extending from the tail 3′ of the surfboard 1′ to both the side edges 4′ and 4′ and at the same time cutting it in half to form two divided pieces symmetrical in shape left and right in the lateral direction of the surboard, and also cutting the through hole 6′ aligned with each mounting hole 5 a in the front and rear sockets 5′ and 5′ for inserting the tabs of the fin, along on the central axis to form two mutually opposite half circle holes 6 a′ and 6 a′. The resultant respective two divided pieces are adhered symmetrically left and right to the rear area 2 a′ of the surfboard 1′ so as to leave a space S at the center portion of the rear area 2 a′, as shown in FIG. 15, so that a surfboard A6 of the present invention is constructed. Alternatively, as shown in FIG. 16, surfboard A7 may be constructed in such a manner that the patterned adhesive film 7A for adhering to a bottom surface is composed of three divided pieces 7 a, 7 a and 7 a by cutting the same into three, and the three divided pieces are adhered so as to leave a space S between the mutually adjacent ones and to be symmetrical in the lateral direction right and left with the center axis line being as the center line.

Furthermore, in general, as for the patterned synthetic resin film for adhering to a fin, instead of the aforementioned adhesive film provided with the adhering face 8 in advance on the rear surface thereof, it is optional that there is prepared, though not shown, a similarly patterned synthetic resin film for adhering to a fin that is not applied with the adhering face 8 in advance to the rear surface thereof, or plural divided pieces prepared by cutting it, and the synthetic resin film or the pieces thereof thus prepared is/are adhered, though not shown, to both the side faces of the fin, after the adhering agent such as the bonding agent or the adhesive agent is coated partially or wholly on both the side faces of the fin of the surfboard body. Furthermore, as for any films of the patterned synthetic resin films for adhering to a bottom surface with or without the coated face of the pressure sensitive adhesive agent on the rear surface thereof, or any films of the patterned synthetic resin films for adhering to a fin with or without the coated face of the pressure sensitive adhesive agent film provided with the coated face, there is prepared such various kinds of synthetic resin films having the surface smoothness that are made of a transparent film, a semi-transparent film, an opaque film, a colorless film or a colored film colored in a desired color, a printed film with any desired indication such as a character, pictures, a pattern, etc., and various kinds of surfboards according to the present invention can be produced by selecting from the above-mentioned various kinds of films and adhering to the rear area of the surfboard body and the fin. For example, a consumer such as a surfer can select and use any desired ones for adhering to the rear area or for adhering to the fin from the various kinds of the synthetic resin films for adherence and the adhesive films according to one's taste or purpose.

Next, in order to compare the above-mentioned various surfboards according to the invention and the conventional surfboard for a speed performance at the time of sliding on water, sliding tests were carried out as follows, using an experimental apparatus as shown in FIG. 19. As for each of the respective surfboards used for the comparison tests, there was used a model that had one third scale of a full size of the actual surfboard, and that was fabricated using the same materials as those used for fabricating the actual surfboard.

More specifically, a model of the surfboard A2 of the present invention as shown in FIG. 4 was prepared as a sample A, a model of the surfboard A4 as shown in FIG. 9 was prepared as a sample B, and a model of the surfboard A5 of the present invention as shown in FIG. 12 was prepared as a sample C. On the other hand, for comparison, a model of the conventional surfboard 1′, namely, which comprises the surfboard body 1′ that was fabricated by using the urethane foam core having an ultra high density in which the stringer is embedded, the surface-polished outer skin of glass fiber-reinforced acrylic plastic material laminated on and integrally laminated on the surface thereof, and the three fins fabricated by the same materials as these of the surfboard body and disposed on the surfboard body, was prepared as a sample D.

On the other hand, as the experimental apparatus, there was prepared an experimental apparatus 14 as shown in FIG. 19. The apparatus 14 is provided with an acceleration slope 16 having a height of 6 feet provided in a rectangular water tank 15 on the left side in the drawing, and a siding course 17 having a total length of 10 feet, and filled with water up to a depth of 600 mm on the right side and the lower end of the acceleration slope 16.

And, for investigating the sliding performance of each of the samples A, B, C and D, one's hold of each sample was released from the same height of the upper portion of the acceleration slope 16, so that each sample may be accelerated in speed and landed on the water and slid on the water surface of the sliding course 17 as illustrated, and a sliding lapsed time (second) was measured at each position by a measuring apparatus from a landing position (0 feet), to the respective points of 2 feet, 4 feet, 5 feet, 6 feet, 8 feet and 10 feet where its sliding was terminated with its collision with the end wall of the water tank. Such a sliding test was repeated 10 times for each sample. In the drawing, A lapsed time (second) at each position for each of the surfboards A, B, C and D indicates the mean value measured in the test of 10 times.

As shown in the drawing, the conventional surfboard D stopped sliding at a position of 7.6 feet from the landing position, and could not slide the whole distance of 10 feet. A lapsed time reaching the position spent 4.8 seconds.

In contrast therewith, the surfboard A of the present invention was such that, for example, a lapsed time reaching a position of 5 feet was 1 second, which means twice the speed of the conventional surfboard D, and that it slid the whole distance of 10 feet. A lapsed time for sliding the whole distance was 5.1 seconds.

The surfboard B of the present invention was such that a lapsed time reaching a position of 5 feet was 0.8 second, and thus the sliding time was made shorter than the surfboard A of the present invention, and that it slid the whole distance of 10 feet, and a lapsed time for sliding the whole distance of 10 feet was 4.4 seconds, and thus improvement in the speed performance was more increased than the surfboard A.

The surfboard C of the present invention was such that a lapsed time reaching a position of 5 feet was 1.8 seconds, and thus was improved in speed as compared with the conventional surfboard D, and its sliding up to 10 feet was fulfilled, and a lapsed time for sliding the distance of 10 was 7.9 seconds.

As will be clear from the foregoing, it has been confirmed that the surfboards A, B and C of the present invention were all improved in speed as compared the conventional surfboard D. Further, The degree of speed improvement of the surfboards of the present invention was increased in the order of the surfboard B, the surfboard A and the surfboard C. Namely, it has been found out that in the case where the synthetic resin film was adhered to both of the bottom surface and the fin of the surfboard, the effect of improvement in speed becomes largest, and it becomes smaller in the order of the case where it was adhered to the bottom surface alone and the case where adhered to the fins alone.

INDUSTRIAL APPLICABILITY

Thus, the present invention is applicable to various kinds of the conventional surfboards, and at the time of sliding on water, it can achieve an improvement in the sliding speed and accordingly an improvement in movement performance such as an improved swiftness of change of direction, etc.

Further, a consumer such as a surfer can select any desired one from various kinds of the synthetic resin films or adhesive films for adhering to surfboards according to the present invention made of such a transparent film, a beautifully colored one, ones with various characters or designs on the surface thereof according to one's discretion, and adheres it to the conventional surfboard, so that he can enjoy the improved speed thereof, and also a design effect bearing on the films, and in addition of its design, the synthetic films according to the present invention can also be utilized for propaganda or advertisement of goods. 

1. A surfboard characterized in that a tough and flexible synthetic resin film having a surface smoothness so patterned as to be adaptable to adhere to a rear area of a water contact bottom surface of a surfboard or/and both side faces of a fin is adhered through an adhering agent such as a bonding agent or an adhesive agent to the rear area of the water contact bottom surface of the surfboard or/and both side faces of a fin.
 2. A surfboard according to claim 1, wherein the synthetic resin film for adherence is selected from a group of polyester resin, polyamide resin, polyethylene resin, polypropylene resin, polyacrylate resin, polycarbonate resin, ABS resin, fluorinated resin and polyvinyl chloride resin.
 3. A surfboard according to claim 1, wherein a degree of a surface smoothness of the synthetic resin film for adherence is a glossy surface smoothness having such a height difference that is less than 0.2μ throughout the whole surface thereof.
 4. An adhesive film for a surfboard comprising a tough and flexible synthetic resin film for adherence having a surface smoothness so patterned as to be adaptable to be adhered to a rear area of a water contact bottom surface of a surfboard or both side faces of a fin, an adhering face formed by coating an adhesive agent on the rear surface of the film, and a released paper temporarily adhered to the adhering face.
 5. An adhesive film for a surfboard according to claim 4, wherein the adhering face is formed by partially coating the adhesive agent regularly or irregularly so that a lot of air escape grooves communicating to the exterior air be formed between a lot of the coated portions.
 6. An adhesive film for a surfboard according to claim 4, wherein the adhesive film for the surfboard is composed of plural divided pieces.
 7. An adhesive film for a surfboard according to claim 4, wherein the film for the surfboard is any kind of films such as a transparent one, an opaque one, a colorless one, a colored one in a desired color, a printed one indicating any desired characters or design on the surface thereof or a desired combination thereof.
 8. A surfboard according to claim 1, wherein the adhesive film for a surfboard comprises a tough and flexible synthetic resin film for adherence having a surface smoothness so patterned as to be adaptable to be adhered to a rear area of a water contact bottom surface of a surfboard or both side faces of a fin, an adhering face formed by coating an adhesive agent on the rear surface of the film, and a released paper temporarily adhered to the adhering face, with the released paper thereof peeled off, adhered to the rear area of the water contact bottom surface of the surfboard and/or to both side faces of the fin(s).
 9. A surfboard according to claim 1, wherein the tough and flexible synthetic resin film having a surface smoothness so prepared as to be adaptable to adhere to the rear area of the water contact bottom surface of the surfboard is so adhered to the rear surface as to become symmetrical on both sides of the central axis of the surfboard.
 10. A surfboard according to claim 1, wherein the tough and flexible synthetic resin film having a surface smoothness so prepared as to be adaptable to adhere to the rear area of the water contact bottom surface of the surfboard is cut into plural pieces and the plural divided pieces are so adhered to the rear surface as to become symmetrical on both sides of the central axis of the surfboard.
 11. An adhesive film for a surfboard according to claim 5, wherein the adhesive film for the surfboard is composed of plural divided pieces.
 12. An adhesive film for a surfboard according to claim 5, wherein the film for the surfboard is any kind of films such as a transparent one, an opaque one, a colorless one, a colored one in a desired color, a printed one indicating any desired characters or design on the surface thereof or a desired combination thereof.
 13. An adhesive film for a surfboard according to claim 6, wherein the film for the surfboard is any kind of films such as a transparent one, an opaque one, a colorless one, a colored one in a desired color, a printed one indicating any desired characters or design on the surface thereof or a desired combination thereof.
 14. An adhesive film for a surfboard according to claim 11, wherein the film for the surfboard is any kind of films such as a transparent one, an opaque one, a colorless one, a colored one in a desired color, a printed one indicating any desired characters or design on the surface thereof or a desired combination thereof.
 15. A surfboard according to claim 2, wherein the adhesive film for a surfboard comprises a tough and flexible synthetic resin film for adherence having a surface smoothness so patterned as to be adaptable to be adhered to a rear area of a water contact bottom surface of a surfboard or both side faces of a fin, an adhering face formed by coating an adhesive agent on the rear surface of the film, and a released paper temporarily adhered to the adhering face, with the released paper thereof peeled off, adhered to the rear area of the water contact bottom surface of the surfboard and/or to both side faces of the fin(s).
 16. A surfboard according to claim 3, wherein the adhesive film for a surfboard comprises a tough and flexible synthetic resin film for adherence having a surface smoothness so patterned as to be adaptable to be adhered to a rear area of a water contact bottom surface of a surfboard or both side faces of a fin, an adhering face formed by coating an adhesive agent on the rear surface of the film, and a released paper temporarily adhered to the adhering face, with the released paper thereof peeled off, adhered to the rear area of the water contact bottom surface of the surfboard and/or to both side faces of the fin(s). 